A year ago, Cuauhtemoc Cardenas was the modern-day dragon slayer of Mexican politics. The leftist opposition leader, son of a political legend, had been installed as the first elected mayor of Mexico City and he led all polls as the choice for president in 2000.

Today, Cardenas's hopes are sinking fast, dragged down by his failure to solve Mexico City's vexing problems, his drab leadership style and dissension and corruption in the political movement he founded, the Democratic Revolutionary Party (PRD).

"Mexico City is his tomb instead of his springboard to higher office," said political analyst Denise Dresser, noting that Cardenas's term as the second-most powerful elected leader in Mexico has not been the presidential steppingstone many thought it could be. "His governing style is like floating in a pool on his back, and he has not resolved the key issues--crime and security."

Cardenas's rapid decline in the polls is transforming the race for president next July, when the ruling Institutional Revolutionary Party (PRI), which has run Mexico for 70 years, is facing one of its toughest challenges ever. Instead of a three-man race, the campaign increasingly is shaping up as a two-man contest between Vicente Fox of the right-center National Action Party (PAN) and whoever emerges as the PRI nominee in the party's November primary. The two front-runners are Francisco Labastida Ochoa and Roberto Madrazo.

Cardenas's slide is forcing him to reach out to Fox to create an opposition alliance, something the two leaders and their parties have been reluctant to do because of huge ideological differences and because of animosity between Fox and Cardenas.

There have been meetings and proposals and vows to find a middle ground, with most energy focused on how to bridge differences on key issues such as privatizing the national oil company and how to select a unity candidate. But many doubt the sincerity of the effort.

Many political analysts question whether Fox or Cardenas, both of whom have aspired to Mexico's highest office for years, would back out of the race and agree to a coalition led by the other. With Cardenas's weakness, he probably would have to be the one stepping aside.

Fox leads in many voter surveys--some by as much as 10 percentage points--perhaps encouraging his belief that he can win the presidency without the compromises needed to cement an alliance. Furthermore, not having a presidential candidate under its own banner could damage the future viability of either party.

On the other hand, polls and recent election results show that it is highly unlikely any opposition party could win a three-way race against the PRI, but that a coalition candidate of a united opposition would likely defeat the ruling party's candidate in a two-way race. If the two parties do not unite, whichever comes in third could be accused of being a spoiler that perpetuated the PRI's grip on power.

Many observers caution that it is too early to count Cardenas out, noting his history of improbable but strong political comebacks. But of the likely presidential candidates, recent polls show he has slipped from first to last place, while his party's share of the prospective presidential vote in 2000 plummeted from 37.5 percent in July 1998 to 16.2 percent last month, according to a survey by Indemerec Louis Harris.

The PRI, apparently alarmed at Cardenas's slipping popularity and his overtures to Fox, seems to be tempering its criticism of the Mexico City mayor, concerned that his drop in the polls could spur a coalition, according to several political analysts and consultants. This week, Labastida goaded Cardenas for selling out his principles for political expediency, apparently referring to the coalition talks.

In an interview, Cardenas said he could not explain his decline in voter surveys, adding that there was an "erroneous" view that the capital had not progressed under his stewardship, and that polls might be reflecting this "disinformation." One of the many factors that have contributed to the capital's problems, Cardenas and other analysts said, is the federal government's decision to cut its contribution to the city's budget this year by $600 million.

In his favor, Cardenas has not been scarred by personal scandal, and he scores well in most surveys for honesty and integrity. But his party, which he founded in 1988 with other PRI dissidents and opposition leaders wanting to open Mexico's political system, was severely damaged in March when its internal leadership elections were nullified because of vote rigging and corruption. The scandal also made the PAN suspicious of whether the PRD could be trusted to participate in a clean selection process for a coalition candidate.

But Cardenas's tenure as mayor of Mexico City--and his inability to curb the capital's soaring crime, police corruption, pollution, unemployment and other problems--has left him vulnerable to charges of ineffectiveness. In a June poll of residents of the capital by the newspaper Reforma, more than 80 percent said crime, pollution and unemployment have stayed the same or gotten worse under Cardenas, and 64 percent said he should not seek the presidency.

The Candidates

Vicente Fox

National Action Party (PAN)

Right-center opposition candidate and former Coca-Cola executive. Once in third place, he now leads many voter surveys. In 1994 presidential election, the PAN candidate came in second, and the party expanded seats in the Chamber of Deputies, where it is the third-largest party.

Cuauhtemoc Cardenas

Democratic Revolutionary Party (PRD)

Leftist opposition leader and the first elected mayor of Mexico City. He led all polls as presidential candidate last year but recently has fallen into third place.

Francisco Labastida Ochoa

Institutional Revolutionary Party (PRI)

Believed to be President Ernesto Zedillo's choice as his successor. But the PRI's support has eroded over its handling of the economy and its history of corruption. Recent reforms have made Mexico's electoral process more democratic and have increased the opposition's chances.

Roberto Madrazo

(PRI)

Governor of Tabasco state, has deep family ties in the PRI, but is campaigning against the party establishment.

A Harris poll conducted in late July showed these results, given the following combinations of candidates if elections were held now:

Fox 37%

Labastida 34%

Cardenas 17%

Madrazo 39%

Fox 34%

Cardenas 18%

Any opposition alliance candidate 51%

Any PRI candidate 43%